This invention relates generally to image processing. More particularly, this invention relates to a method for converting printed maps into digitally stored images of a unique format.
Computer systems that can generate and display geographic map images are now commonly available. Typically a computer system that provides map images has stored within its memory system, such as in secondary storage, data corresponding to the map images. The map image data, if stored as bit maps, may be then be directly retrieved for display. Or the map image data may be stored as information within a database, and the computer system may independently generate a map image from the database information.
An increasingly popular use of computer-generated map images is for graphical navigation systems, such as xe2x80x9cmoving mapxe2x80x9d systems. Pioneer Electronics of Tokyo, Japan, for example has designed a moving map system for vehicles such as automobiles. A moving map system receives data from the Global Positioning System (GPS) satellites to determine the vehicle""s current location. The moving map system uses this data to select geographic data stored in the system, such as on a CD-ROM, and retrieves therefrom a map image of the current location for display. The map image is actually a changing combination of several images that are generated as the vehicle moves from one geographic location to another, giving the appearance that the map is moving. A cursor on the map image shows the current vehicle location to the vehicle operator and allows him to navigate with the map image.
A drawback of present computer systems for displaying map images is the poor quality of the map images they display. In systems that generate map images from data within a database, the detail of the map image is sparse. Only those geographic objects that are recorded within a database field appear on the image. For example, a map database may contain fields for locating objects on the map, but not provide a field for displaying topological features such as elevations and valleys. On the other hand, systems that store detailed map images as bit maps do not store the images in a uniform format. Without a uniform format, the bit mapped images vary in size, making it difficult to accurately determine and display a vehicle""s location on the map image. The varying size also leaves gaps on the screen as an image of one size is replaced by an image of another size. The various images are like poorly fitting pieces of a puzzle that cannot be pieced together without gaps between them.
An object of the invention, therefore, is to provide a method for providing highly detailed map images in a uniform format. This format should allow the computer system to display a cursor (i.e., a point of interest) on the map image to accurately show a vehicle""s geographic location. This format should also allow the map images to seamlessly fit together so that no gaps appear on the display as one image is replace by another. When used in a moving map system, the map images should give the appearance of a unified image as the vehicle moves from one geographic area to another across individual map images. Another object of the invention is to provide an apparatus on which map images of a uniform format are stored for easy retrieval into a computer system.
These and other objects of the invention will become more apparent from the following detailed description of a preferred embodiment.
In accordance with the invention, a computer-implemented method of generating digital map images of a uniform format is shown and described. In the method, bit mapped map images corresponding to a printed map are provided. A bit mapped map image is then cropped to select a map image corresponding to a desired geographic area, such as a one degree by one degree square. The boundaries of the selected map image are selectively moved to shape the geographic area into a tessellated shape, such as a rectangle. The selected map image is then re-sized to contain a predetermined pixel area. The map image, now of a uniform format, is then stored with an identifier of a reference point, such as a location, and size of the geographic area represented by the map image. For example, the identifier may be the name of a computer-readable file containing the map image.
The initial bit mapped map image may be obtained from a printed map through scanning or other known techniques for converting printed graphics into electronic images. The desired geographic area may be defined on the map with reference grid lines such as latitude and longitude lines.
An apparatus according to the invention may comprise a storage medium such as a CD-ROM on which are stored a plurality of bit mapped geographic map images in computer readable form. Each image has a predetermined pixel area and an identifier of a reference point and size of the geographic area represented by the map image. The identifier is preferably the name of the image file.
CD-ROMs and other devices imprinted in accordance with the method of the invention provide a unique store of map images which may be used in any number of way. The map images are particularly valuable in moving map systems where it is desirable to view detailed graphic information on a display as a car, plane or other vehicle moves from one geographic location to another. Another valuable use is for constructing and printing custom maps. For example, a number of map images may be retrieved from the CD-ROM and combined into a larger map that covers a planned trip route. The layer map image is then printed.